1. Field of the Invention
The present invention relates to a woven carbon fiber fabric as a precursor for a prepreg, a prepreg produced from the precursor, processes for producing a carbon fiber reinforced composite material from the precursor, a carbon fiber reinforced composite material produced from the precursor, and a process for the production of the carbon fiber reinforced composite material.
2. Description of the Related Art
Since composite materials produced from prepregs consisting of carbon fibers and a matrix resin have excellent mechanical properties, they are widely used in sporting equipment such as in golf clubs, tennis rackets, fishing rods, etc., and in aircraft production as structural materials, and for other applications.
The reinforcing fibers used in carbon fiber reinforced composite materials are usually in the form of woven fabrics which provide excellent formability and mechanical properties. Such a composite material can be produced by overlapping a plurality of prepreg sheets, then heating and hardening the matrix resin to form a composite material. The prepreg sheets are laminated with the carbon fibers oriented in a desired direction, which keeps the formed product void-less and compact. The prepreg must also have moderate tackiness and drapability to assure good handling convenience.
A woven carbon fiber is usually composed of warp and weft threads which are crimped in the thickness direction of the woven fabric. When the woven carbon fiber fabric is impregnated with a matrix resin to make a prepreg, the impregnation pressure flattens the fabric, thus causing a resin layer to be formed on the surface. The viscosity of the resin makes the prepreg moderately tacky. However, the crimped warp or weft threads spring back due to their original shape, resulting in a settlement of the resin on the surface of the prepreg to inside the woven fabric. Therefore, if the prepreg is allowed to stand at room temperature, the amount of resin on the surface of the prepreg decreases which lowers the tackiness of the prepreg. Moreover, if sheets of the prepreg are laminated and formed, the formed product lacks resin on its surface so as to lose smoothness.
JP-A-86-34244 describes a conventional method for stabilizing the structural form of a woven carbon fiber fabric by bonding the intersections of warp and weft threads with copolymer nylon. While this method is effective for securing the meshes of the weave and preventing the woven threads from being frayed in the carbon fiber woven fabric, it fails to keep the prepreg tacky for an extended time.